The messages were part of Mr Khashoggi’s correspondence with Canada-based activist Omar Abdulaziz.

In one message from May, after multiple arrests of Saudi activists, Mr Khashoggi wrote: “arrests are unjustified and do not serve him … but tyranny has no logic, but he loves force, oppression and needs to show them off.

Mr Khashoggi, a columnist for the Washington Post who had lived in the US state of Virginia, was killed by Saudi operatives shortly after entering the consulate. He had gone there seeking papers needed to marry his Turkish fiance.

“The hacking of my phone played a major role in what happened to Jamal, I am really sorry to say,” Abdelaziz told CNN.

“The guilt is killing me.”

The almost-daily exchanges from October 2017 to August 2018 between Mr Khashoggi and Mr Abdelaziz show the pair had plans to form an online army to engage Saudi youth back home.

In August, Mr Abdulaziz told Business Insider that the Saudis had targeted two of his brothers and some of his friends in response to his political activism.

Mr Abdulaziz is a strong voice on Twitter with more than 341,000 followers. He has spoken out multiple times against the Saudi monarchy and the kingdom’s poor human rights record.

In August he claimed Saudi authorities approached some of his friends and family in an attempt to muzzle Mr Abdulaziz and stop his criticism of the government from his residence in Montreal.

Mr Abdulaziz applied for political asylum in 2014 citing that his criticism of the Saudis posed safety risks. This was approved and he was granted permanent residency in Canada in 2017.

“I was scared to go back to my country,” he told Business Insider.

“I knew that if I went back I would be imprisoned.”

Canada’s relationship with the Saudi kingdom is strained. In August Canadian foreign minister Chrystia Freeland called out the Saudi’s human rights record in a tweet after the activist crackdown.

Canada has announced sanctions against 17 Saudi nationals it believed were linked to the Khashoggi case. Picture: AFPSource:AFP

The Saudis’ response was dramatic; they expelled the Canadian ambassador, froze trade, cancelled flights to Toronto and pulled thousands of students from Canadian institutions.

Yesterday it was revealed Mr Abdulaziz had filed a lawsuit against an Israeli software company he says helped Saudi authorities to monitor him, including his dealings with Mr Khashoggi, through use of spyware.

Amnesty International also recently accused the tech firm, NSO Group, of helping the Saudis to spy on one of their staff.

In a statement published by The New York Times, NSO Group said its products were “licensed for the sole use of providing governments and law enforcement agencies the ability to lawfully fight terrorism and crime.”

Candles lit by activists protesting the killing of Jamal Khashoggi, placed outside the consulate building in Istanbul. Picture: AFPSource:AP

It said misuse of its software was not tolerated: “If there is suspicion of misuse, we investigate it and take the appropriate actions, including suspending or terminating a contract.”

The spyware - known as Pegasus - is capable of reading text messages, tracking calls and internet history, collecting passwords, tracking the location of a phone and gathering information from apps. It can also enable use of the phone’s microphone and camera as surveillance devices.

The WhatsApp messages come as it was revealed that Mohammed bin Salman sent at least 11 messages to his closest adviser who has been linked with those said to be involved in Mr Khashoggi’s murder.

According to the Wall Street Journal, who quote a CIA assessment, the crown prince also allegedly told his associates in August 2017 that if he failed to persuade Mr Khashoggi to return to Saudi Arabia ““we could possibly lure him outside Saudi Arabia and make arrangements.”

Saudi King Salman presents President Donald Trump with the highest civilian honour, the Collar of Abdulaziz Al Saud, at the Royal Court Palace, in Riyadh in 2017. Picture: APSource:AP

The WSJ highlights that the CIA assessment indicates that this “seems to foreshadow the Saudi operation launched against Khashoggi.”

This comes after the CIA concluded in November that it was likely that the crown prince had ordered Mr Khashoggi’s killing, however Donald Trump questioned this finding, stating: “maybe he did, and maybe he didn’t.” President Trump has been accused of covering for the Saudi monarchy.

Tunisians demonstrate with saws in Tunis amid international concern about the killing of Jamal Khashoggi. Picture: Hassene DridiSource:AP

The Saudis, who repeatedly denied the murder, eventually admitted some liability but blamed the killing on a “rogue” operation.

The WSJ claimed it had reviewed excerpts of the highly classified CIA document, which relied on electronic intercepts and other clandestine information. It claimed the CIA has “medium-to-high confidence” the crown prince had “personally targeted” Mr Khashoggi and “probably ordered his death.”

But the document stopped short of stating this as a firm fact, adding: “To be clear, we lack direct reporting of the Crown Prince issuing a kill order.”

The cited messages were said to be sent by the crown prince to former royal court adviser Saud al-Qahtani on October 2, the day of Mr Khashoggi’s murder.

Saud al-Qahtani served as a media adviser and to MBS and was considered one of his closest aides. He is also allegedly responsible for overseeing an assassination plot against Mr Khashoggi.

The CIA says Saudi Crown Prince Mohammed bin Salman is probably linked to the killing, but Donald Trump has distanced himself from those accusing the crown prince of involvement. Picture: APSource:AP

It’s thought that he supervised the 15-man team that carried out the killing.

The contents of the messages between MBS and Saud al-Qahtani are unknown. The method of electronic communication used between the pair were not revealed either.